The 99-year-old war veteran who has raised £29m for the NHS by walking laps of his garden has been honoured with a special postmark.
Royal Mail will stamp all letters with the message to celebrate Captain Tom Moore's 100th birthday on Thursday.
All stamped post up until Friday will be marked with: "Happy 100th Birthday Captain Thomas Moore NHS fundraising hero 30th April 2020."
Royal Mail said it was "honoured" to issue the postmark.
World War Two veteran Capt Tom, from Marston Moretaine in Bedfordshire, has extended his challenge to 200 laps after he completed the first 100 laps 14 days ahead of schedule.
His initial £1,000 fundraising target was broken in about 24 hours and he has now raised more than £29m for the NHS.
David Gold, director of public affairs and policy at Royal Mail, said: "What Captain Thomas Moore has achieved is truly phenomenal, and this is reflected in the affection shown for him across the world.
"As Royal Mail works to keep the country connected during these challenging times, we are honoured to issue a special postmark in celebration of his 100th birthday."
Royal Mail said it had to adapt its sorting machines in the South Midlands Mail Centre to re-route all post to Capt Tom into a dedicated collection box.
A spokesman said staff had already processed more than 100,000 cards using this new process and were expecting thousands more in the run-up to his birthday.
Volunteers have also been brought in to open and display the thousands of cards, which are being put on show at Bedford School where Capt Tom's grandson attends.
On Friday it was revealed Capt Tom would be the first ever centenarian to top the charts, after his duet with Michael Ball went straight to number one.
Their cover of You'll Never Walk Alone sold 82,000 copies, with proceeds going to the NHS Charities Together fund.
Capt Tom also opened a new Nightingale Hospital in Harrogate on Tuesday.
He received a standing ovation from NHS staff and military personnel during the virtual ceremony.